Generally, a secondary battery refers to a rechargeable battery, while a general battery refers to a non-rechargeable battery. Secondary batteries are widely used for electronic devices such as cellular phones, notebook computers, video cameras, electric vehicles, or the like. In particular, a lithium secondary battery has an operating voltage of about 3.6 V, triple the capacity of nickel-cadmium batteries or nickel hydrogen batteries generally used as power sources of electronic devices, and due to its high energy density per unit weight, are being utilized more and more.
The lithium secondary battery generally uses lithium oxide and carbonaceous material as cathode active material and anode active material, respectively. The lithium secondary battery includes an electrode assembly in which a cathode plate and an anode plate respectively coated with the cathode active material and the anode active material are disposed with a separator being interposed between them, and an exterior material which seals and receives the electrode assembly together with an electrolyte.
Meanwhile, the lithium secondary battery may be classified into a can type secondary battery where the electrode assembly is included in a metal can and a pouch type battery where the electrode assembly is included in a pouch of an aluminum laminate depending on the shape of the battery case. In addition, the can type secondary battery may further be classified into a cylindrical battery and a rectangular battery depending on the shape of the metal can.
The electrode assembly is classified into a jelly roll type electrode assembly where a separator is interposed between the cathode plate and the anode plate and then rolled, and a stack type electrode assembly where separators are interposed between a plurality of cathode plates and anode plates with a predetermined size and then successively laminated. The stack type electrode assembly is generally used for a pouch type battery, and the jelly roll type electrode assembly is generally used for a can type secondary battery. In particular, the jelly roll type electrode assembly is widely used due to its advantages such as easy fabrication, high energy density per weight, and easy storage in a cylindrical or rectangular battery can.
In the jelly roll type electrode assembly, also called “jelly roll” due to its shape, the cathode plate, the anode plate and the separator are laminated and rolled. Here, a seal tape is attached to the outermost terminal or a rolling end of the electrode assembly, so that the electrode assembly may maintain its rolled state without being released. In addition, the electrode assembly to which the seal tape is attached as described above is received in a metal can together with an electrolyte, and a cap assembly having an electrode terminal is coupled to the upper opening end of the battery case.
However, the secondary battery having the above configuration has a problem in that the electrode assembly may move vertically or horizontally in the battery if the battery falls or external impact is applied thereto. Such movement of the electrode assembly may cut a tap connected between the electrode assembly and the cap assembly, which may cause a power insensitive phenomenon of the secondary battery. In addition, the vertical movement of the electrode assembly presses the upper or lower portion of the electrode assembly to deform the electrode assembly and cause a short circuit, which may break the secondary battery and lead to accidents such as firing or explosion, causing great damage. Moreover, the vertical movement of the electrode assembly may give impact to the cap assembly coupled to the upper opening portion of the secondary battery, causing the sealing portion to break or separate, which may lead to the electrolyte in the secondary battery to leak.